B-Anomalies from flavorful U(1)' extensions, safely

Abstract

$U(1{)}^{\prime }$ extensions of the standard model with generation-dependent couplings to quarks and leptons are investigated as an explanation of anomalies in rare $B$-decays, with an emphasis on stability and predictivity up to the Planck scale. To these ends, we introduce three generations of vector-like standard model singlet fermions, an enlarged, flavorful scalar sector, and, possibly, right-handed neutrinos, all suitably charged under the $U(1{)}^{\prime }$ gauge interaction. We identify several gauge-anomaly free benchmarks consistent with $B_s$-mixing constraints, with hints for electron-muon universality violation, and the global $b\to s$ fit. We further investigate the complete two-loop running of gauge, Yukawa and quartic couplings up to the Planck scale to constrain low-energy parameters and enhance the predictive power. A characteristic of models is that the $Z^{\prime }$ with TeV-ish mass predominantly decays to invisibles, i.e. new fermions or neutrinos. $Z^{\prime }$-production can be studied at a future muon collider. While benchmarks feature predominantly left-handed couplings $C_9^{\mu }$ and $C_{10}^{\mu }$, right-handed ones can be accommodated as well.

Comments: 22 pages, 15 figures, v2: match published version